Synthesis and properties of air-stable 1,3-diphosphacyclobutane-2,4-diyls and the related compounds

A kinetically stabilized phosphaalkyne bearing a bulky Mes^∗ (2,4,6-tri-t-butylphenyl) group is useful compound to prepare an enormous number of highly stable 1,3-diphosphacyclobutane-2,4-diyls through reactions with a lithium reagent and an electrophile. By utilizing this synthetic protocol, we prepared several non-symmetrical 1,3-diphosphacyclobutane-2,4-diyls in which the substituents on the phosphorus are different. Furthermore, we succeeded in preparation and characterization of novel air-tolerant symmetrical 2,4-bis(2,4,6-tri-t-butylphenyl)-1,3-diphosphacyclobutane-2,4-diyls bearing the identical alkyl substituents on the phosphorus atoms. Structures and properties of the 1,3-diphosphacyclobutane-2,4-diyls indicate characters as singlet ground-state carbon centered biradicals. In addition to those biradicals, we succeeded in preparation and isolation of a novel P-heterocyclic air-stable neutral radical as well as a P-heterocyclic cation radical.     

Preparation and reactions of 1,3-diphosphacyclobutane-2,4-diyls that feature an amino substituent and/or a carbonyl group

The preparation and properties of a 1-amino-1,3-diphosphacyclobutane-2,4-diyl and a 1-benzoyl-1,3-diphosphacyclobutane-2,4-diyl, which can be regarded as functionalized cyclic biradical derivatives, were investigated. Hydrolysis of 1-diisopropylamino-3-methyl-2,4-bis(2,4,6-tri-tert-butylphenyl)-1,3-diphosphacyclobutane-2,4-diyl (7), which is formed by reaction of Mes*C[triple chemical bond]P (4; Mes*=2,4,6-tBu(3)C(6)H(2)) with lithium diisopropylamide and iodomethane, resulted in ring-opening of the 1,3-diphosphacyclobutane-2,4-diyl skeleton, as well as de-aromatization of one of the Mes* rings. 3-Oxo-1,3-diphosphapropene 8 and 7-phosphabicyclo[4.2.0]octa-1(8),2,4-triene 9 were the resultant products, and these were subsequently characterized. Isomerization and oxidation of 7 occurred in the presence of TEMPO (2,2,6,6-tetramethyl-1-piperidinoxy) to give the first example of a cyclic dimethylenephosphorane derivative, namely 3-oxo-1,3-diphospha-1,4-diene 10. 1-Benzoyl-3-tert-butyl-2,4-bis(2,4,6-tri-tert-butylphenyl)-1,3-diphosphacyclobutane-2,4-diyl (12) was isolated and characterized from the reaction of 4 with tert-butyllithium and benzoyl chloride. Compound 12 was subsequently heated and underwent rearrangement of the benzoyl group and ring-expansion to afford 1-oxo-1H-[1,3]diphosphole 13. Reaction of 4 with lithium diisopropylamide and benzoyl chloride afforded the 2H-[1,2,4]oxadiphosphinine 15, which was probably formed through the 1,3-diphosphacyclobutane-2,4-diyl intermediate 14. Thermolysis of 15 afforded 1-oxo-1H-[1,3]diphosphole 16 in an Arbuzov-type rearrangement.     

1,3-Diborata-2,4-diphosphoniocyclobutane-1,3-diyls communicate through a para-phenylene linker

The presence of a second 1,3-diborata-2,4-diphosphoniocyclobutane-1,3-diyl in the para-position of a phenylene linker favors the diradical form over the 1,3-diborata-2,4-diphosphoniobicyclo[1.1.0]butane bond stretch isomer, as long as the two planar diradical units are coplanar with the linker. This demonstrates that two BPBP diradicals communicate through the phenyl ring.     

Synthesis and physicochemical properties of polysiloxane functionalized with aminoacetic acid groups

Polysiloxane functionalized with aminoacetic acid groups was synthesized using sol–gel technology. Elemental analysis and FTIR spectroscopy were used to determine the composition of the polysiloxane show that it is a mesoporous material with a developed surface (109.4 m2/g). It was found that the selective properties of carboxymethylated polysiloxane towards transition metal ions simultaneously present in an ammonium acetate solution change in the order Zn < Cu > Ni > Co > Pb > Cd. It was shown that the sorption of copper(II) ions by carboxymethylated aminopropylpolysiloxane with particle sizes of 50–71 μm reaches its maximum level within 2 h; the rate-limiting step of the process is the chemical reaction between the ions and the polysiloxane functional groups; and the pseudo-second-order model is the best way of describing sorption.     

Synthesis of an optically active helical poly(1,3-phenyleneethynylene) bearing stable radicals and its chiroptical and magnetic properties

We synthesized an optically active helical poly(1,3-phenyleneethynylene) with pendant galvinoxyl residues and dimethyl(10-(1S)-pinanyl)silyl groups. The hydrogalvinoxyl precursor polymer was given by polymerization of (1,3-diiodophenyl)hydrogalvinoxyl and 1,3-diethynyl-5-[dimethyl(10-(1S)-pinanyl)silyl]benzene using Pd(PPh₃)₄ catalyst (M_w = 1.7 × 10⁵, M_w/M_n = 3.7). In the CD spectrum taken in ethyl acetate solution, clear Cotton effects were observed in the absorption region of the backbone and hydrogalvinoxyl chromophore, indicating an excess of one-handed helical foldamer conformation. The polymer yielded the corresponding polyradical with high spin concentration by treatment of the polymer solution with PbO₂. The Cotton effects appeared in CD spectra of the polymer and polyradical by addition of methanol to the chloroform solution, although the Cotton effects were hardly observed in chloroform. On the other hand, in the MCD spectra of the polymer and polyradical taken in chloroform solution, Faraday effects were observed in the absorption region of the backbone and galvinoxyl chromophore. The static magnetic susceptibility of the chiral polyradical was measured using a SQUID magnetometer, and showed the antiferromagnetic interaction.     

Synthesis and properties of thermally stable polyimides bearing pendent fluorene moieties

A new diamine monomer containing fluorene unit, 3,5‐diamino‐N‐(9H‐fluoren‐2‐yl)benzamide was successfully synthesized via the condensation of 2‐aminofluorene and 3,5‐dinitrobenzoyl chloride and subsequent reduction of the dinitro compound. A series of novel aromatic polyimides having pendent fluorenamide moieties were prepared from the reaction of the diamine monomer and various tetracarboxylic dianhydrides by a conventional two‐step polymerization process. The polyimides were obtained in quantitative yields with inherent viscosities of 0.33–0.44 dl/g. The resulting polymers dissolved in N‐methyl‐2‐pyrrolidinone, N,N‐dimethylacetamide, N,N‐dimethylformamide, and dimethyl sulfoxide. The glass transition temperature of these polymers was in the range of 261–289°C. They were fairly stable up to a temperature around 450°C and lost 10% weight in the range of 498–556°C in nitrogen. The UV–vis absorption spectra showed that all of the polymers had absorption maxima around 320 nm. Cyclic voltammograms of the polyimides revealed an oxidation wave with a peak around 1.3 V. Copyright © 2014 John Wiley & Sons, Ltd.     

Synthesis and spectral properties of 1,4-naphthoquinone sulfanyl derivatives

Reactions of 2,3-dichloro-1,4-naphthoquinone with hexadecanethiol and other alkanethiols in ethanol in the presence of sodium carbonate afforded new symmetric and unsymmetrical sulfanylnaphthoquinone dyes.     

Synthesis and fire retardant properties of vinylic polymers bearing phosphonated groups

To overcome the use of halogenated compounds, which are usually incorporated in plastics as flame retardant additives, the authors investigated the synthesis possibilities, to introduce with covalent bonds, the flame retarder groups at different positions of the polymer chains. They established correlations between the topology of the phosphonated groups and the flame retardant properties. They attempt to determine the origin of the flame resistance obtained in several cases. Their goal is to extend their interesting results obtained from oligomers, to polymer of high molecular weight.     

Topics of 1,3-diphosphacyclobutane-2,4-diyl derivatives: Structural aspects and functionality of isolable heavier congeners of cyclobutane-1,3-diyl and the related molecules

This minireview summarizes recent findings on isolable congeners of cyclobutane-1,3-diyl from the views of structural characters, usefulness for organo electronics, and activation of small molecules. Recent findings on isolable cyclopentane-1,3-diyl, 2,4-dimethylene-1,3-cyclobutanediyl, and cyclobutadiene are also overviewed. This article focuses on the reports on the isolable biradicals that have been published since 2013.     

Synthesis and physicochemical properties of organo- and water-soluble octasubstituted phthalocyanines with cyclohexylphenoxy groups

Russian Chemical Bulletin - Synthesis of 4-(4-cyclohexylphenoxy)-5-nitrophthalonitrile was developed. The method was used for the synthesis of cobalt, zinc, and copper...     

Synthesis and chiroptical properties of helical polyallenes bearing chiral cholesteryl pendant groups

A cholesteryloxyallene (1) bearing chiral cholesteryl pendant group was designed and synthesized. Living polymerization of this monomer with an allylnickel complex as a catalyst give poly(cholesteryloxyallene)s (poly‐ 1 _ms) in high yields with controllable molecular weights and narrow molecular weight distributions. These polymers were found to possess a dynamic helical conformation with a preferred handedness in n‐hexane as confirmed by circular dichroism and absorption spectra as well as optical ratios. The helical conformation of the polymers was revealed to stabilize as the number of repeat units increased until the degree of polymerization reached 100. The helical conformation of poly‐ 1 ₁₀₀ could be controlled by altering the temperature of solutions. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 2227–2233     

Synthesis of soluble oligothiophenes bearing cyano groups, their optical and electrochemical properties

The synthesis and the characterization of twelve new soluble oligothiophenes, possessing two to four 3,4-dicyanothiophene units in their backbone, are described. These semiconductors are prepared through Stille coupling and/or homo-coupling reactions. Cyclic voltammetry studies have been performed to evaluate their stability as n-type semiconducting materials under ambient conditions. The measured electrochemical and optical properties are fully supported by quantum-chemical calculations.     

Synthesis and properties of polyimides bearing acid groups on long pendant aliphatic chains

A series of novel polyimide electrolytes having long pendant sulfo‐ or phosphoalkoxy groups were synthesized for fuel‐cell applications. Sulfodecyloxy‐, phosphodecyloxy‐, and sulfophenoxydodecyloxy‐substituted benzidine monomers were synthesized from dihydroxybenzidine. These monomers were copolymerized with naphthalene tetracarboxylic dianhydride and fluorenylidene dianiline to give the corresponding polyimides. A flexible, ductile, and self‐standing membrane was obtained via casting from the polyimide solution. Because the acid groups were on long pendant side chains and away from the main chains, the polyimide membrane showed improved oxidative and hydrolytic stability in comparison with the polyimides with sulfonic acid groups on the main chains or on the short side chains. High thermal stability (no glass‐transition temperature and a decomposition temperature > 200 °C) was also obtained. The polyimide membrane displayed high proton conductivity of 10^?1 S cm^?1 at 120 °C. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3995–4005, 2006     

Synthesis and photophysical properties of polyfluorenes bearing silicon‐based functional groups

Five polyfluorenes bearing bulky trimethylsilyl (PTMS1 and PTMS2), tris(trimethylsilyl)silyl (PTTMS1), and silsesquioxane groups (PPOSS1 and PPOSS2) were synthesized through palladium‐catalyzed Suzuki coupling reactions. In the solution state, every polymer showed comparable ultraviolet–visible spectra, and they emitted blue light with high quantum efficiency. In the solid state, however, three trimethylsilyl‐functionalized polyfluorenes indicated redshifts of the fluorescence peak. In particular, PTMS1 and PTTMS1, having a hydrogen at the C‐9 position of fluorene, also showed green‐light emissions. After the annealing of the spin‐coated films, the blue‐emissive peak decreased and the green‐emissive peak became stronger in the photoluminescence spectra of three trimethylsilyl‐functionalized polyfluorenes. In contrast, PPOSS2 showed a pure blue‐light emission in the film state and even after the thermal treatment, which could be accomplished by the encapsulation of the polymer chains by the large polyhedral oligomeric silsesquioxane molecule. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2119–2127, 2005     

Synthesis and physicochemical properties of melam

Fusing melamine with 2, 4-diamino-6-chloro-s-triazine gives melam. From its UV and IR spectra, it is assigned structure II. Thermographic studies showed that melam is not an intermediate product, but a side product, of thermal deamination of melamine.     

Synthesis and physicochemical properties of metallobacteriochlorins

Access to metallobacteriochlorins is essential for investigation of a wide variety of fundamental photochemical processes, yet relatively few synthetic metallobacteriochlorins have been prepared. Members of a set of synthetic bacteriochlorins bearing 0-4 carbonyl groups (1, 2, or 4 carboethoxy substituents, or an annulated imide moiety) were examined under two conditions: (i) standard conditions for zincation of porphyrins [Zn(OAc)(2)·2H(2)O in N,N-dimethylformamide (DMF) at 60-80 °C], and (ii) treatment in tetrahydrofuran (THF) with a strong base [e.g., NaH or lithium diisopropylamide (LDA)] followed by a metal reagent MX(n). Zincation of bacteriochlorins that bear 2-4 carbonyl groups proceeded under the former method whereas those with 0-2 carbonyl groups proceeded with NaH or LDA/THF followed by Zn(OTf)(2). The scope of metalation (via NaH or LDA in THF) is as follows: (a) for bacteriochlorins that bear two electron-releasing aryl groups, M = Cu, Zn, Pd, and InCl (but not Mg, Al, Ni, Sn, or Au); (b) for bacteriochlorins that bear two carboethoxy groups, M = Ni, Cu, Zn, Pd, Cd, InCl, and Sn (but not Mg, Al, or Au); and (c) a bacteriochlorin with four carboethoxy groups was metalated with Mg (other metals were not examined). Altogether, 15 metallobacteriochlorins were isolated and characterized. Single-crystal X-ray analysis of 8,8,18,18-tetramethylbacteriochlorin reveals the core geometry provided by the four nitrogen atoms is rectangular; the difference in length of the two sides is ～0.08 ?. Electronic characteristics of (metal-free) bacteriochlorins were probed through electrochemical measurements along with density functional theory calculation of the energies of the frontier molecular orbitals. The photophysical properties (fluorescence yields, triplet yields, singlet and triplet excited-state lifetimes) of the zinc bacteriochlorins are generally similar to those of the metal-free analogues, and to those of the native chromophores bacteriochlorophyll a and bacteriopheophytin a. The availability of diverse metallobacteriochlorins should prove useful in a variety of fundamental photochemical studies and applications.